The Warning Signs That Matter Most When a Very Young Baby Is Unwell

What a 2026 review of 52 studies and more than 140,000 babies, by Driker and colleagues in JAMA Pediatrics, tells families and health workers about spotting serious infection in the first two months of life

Babies in their first two months can become seriously ill from infection very quickly, and in many parts of the world health workers must decide who needs hospital care by looking at the baby rather than by running laboratory tests. A large 2026 review of 52 studies and more than 140,000 babies found that poor feeding, a weak cry, unusual sleepiness and slow return of skin colour after gentle pressure were among the signs most strongly linked to serious illness and death.

The review, led by Driker and colleagues and published in the journal JAMA Pediatrics [1], brings together decades of research into a single picture. It also confirms that the warning-sign checklist used by health workers around the world is built on solid ground, while pointing to a few signs that might make it even better.

Why the first two months are such a delicate time

A newborn's defences against germs are still developing, and infections that an older child might shrug off can quickly become dangerous. Worldwide, nearly half (49.2%) of the 5.30 million deaths among children younger than 5 years in 2019 were caused by infections [2]. Researchers who combined data from sub-Saharan Africa, south Asia and Latin America estimated that about 1 in 10 newborns (9.8%) with a suspected serious bacterial infection died, and noted that treatment is usually decided on the basis of the baby's symptoms and examination alone [3]. In one large study of nearly 250,000 babies born in rural communities in six countries, about 13 in every 100 newborns showed signs of a possible serious infection in their first six weeks [4].

In places where a blood test can take days or is not possible at all, the most important tool a health worker has is a careful look at the baby. That is why knowing exactly which signs matter most is so important.

How health workers learned to read a baby's warning signs

The checklist used today was built step by step over many years. In a study run by the World Health Organization (WHO) at health facilities in Ethiopia, The Gambia, Papua New Guinea and the Philippines, researchers found 14 signs, including feeding problems, unusual drowsiness, grunting, a bluish colour and slow return of colour to the skin, that pointed to severe disease. Looking for any one of them caught most sick babies but also flagged many babies who were not seriously ill [5]. In villages in Gadchiroli, India, trained local health workers learned to spot babies at risk of dying from infection using simple signs such as a weak or absent cry and reduced sucking [6].

The biggest step came with the Young Infant Clinical Signs study (YIS-2) [1], which examined more than 8,800 sick babies under two months old at health facilities in Bangladesh, Bolivia, Ghana, India, Pakistan and South Africa [7]. The researchers narrowed a long list of signs down to seven, choosing them "mainly on the basis of prevalence", in other words largely because they were common enough to be useful. Two signs that were strongly linked to severe illness, slow return of skin colour and a bluish colour, were left out at that stage [7]. Health workers visiting families at home in rural Bangladesh later showed that a slightly adapted seven-sign checklist worked well in the community too [8].

These findings shaped the WHO programme called Integrated Management of Childhood Illness (IMCI), first developed in 1995 and now used in more than 100 countries. Its current seven-sign checklist for possible serious bacterial infection (PSBI), the medical term for a suspected dangerous infection, was published in guidance in 2019 [1]. Later research from the AFRIcan NEonatal Sepsis Trial (AFRINEST), carried out at five sites in the Democratic Republic of the Congo, Kenya and Nigeria, showed that not all checklist signs carry the same risk: among babies aged one week to two months whose only problem was classed as fast breathing, about 2 in every 1,000 died, while signs of critical illness were much more dangerous [9]. Earlier reviews had summarised the evidence in words [10] or tested whole checklists [11], but no one had combined all the studies to measure the importance of each sign on its own.

What the researchers did

The team carried out what is called a systematic review and meta-analysis. In simple terms, they searched medical databases for every study that had looked at warning signs in sick babies up to 59 days old, then combined the results with statistics to get a more reliable answer than any single study could give [1]. They found 52 suitable studies involving 140,885 babies in 30 countries, 21 of them low- or middle-income countries. The studies took place in homes and communities, in clinics and in hospital wards, including neonatal intensive care units (the specialised hospital units for newborns).

The researchers looked at 24 signs that a health worker can see or ask about. For each one, they asked how much more likely babies with that sign were to die, to have bacteria growing in a blood sample (called culture-confirmed sepsis), or to be diagnosed with a serious infection supported by other laboratory tests or X-rays (called clinical sepsis). The results are expressed as "odds", a way of comparing how likely something is in one group than in another.

The warning signs most strongly linked to serious illness

Several signs stood out. Babies with a weak, abnormal or absent cry had about 20 times higher odds of dying than babies without it. Being unable to feed at all was linked to about 18 times higher odds, not feeding well to about 13 times, being drowsy or unconscious to about 12 times, and slow return of skin colour after pressure to about 12 times [1]. Being too cold (a low body temperature) was linked to about four times higher odds of dying.

Poor feeding was the sign most often present in babies who went on to die: about 3 in every 4 of them (74.4%) had been feeding poorly [1]. That makes "how is your baby feeding?" one of the most valuable questions any health worker can ask.

For infections confirmed by a blood test, the links were weaker but still clear, with poor feeding, slow return of skin colour, lethargy (low energy and floppiness), drowsiness and difficulty keeping feeds down leading the list [1]. Interestingly, fast breathing was linked to a higher chance of dying but not to blood infection. That makes sense: newborns can breathe fast for many reasons, including being born early or having a heart problem [12], and a newborn's breathing rate can change a great deal from one minute to the next [13].

Every sign on the WHO checklist was clearly linked to at least one of the three outcomes the researchers studied, which supports the checklist health workers already use [1].

Two important signs that are not on the checklist

The review highlighted two signs that are not part of the current seven-sign checklist. The first is capillary refill, which is how quickly colour returns to the skin after it is pressed gently for a few seconds. When blood flow is poor, colour comes back slowly. Earlier research in children of all ages found that a slow capillary refill was linked to about four times the risk of dying, although a normal result does not rule out serious illness [14]. One challenge is that studies measured it in different ways and in different places on the body [1], and in the first week of life a normal refill can take somewhat longer than in older babies and children [15].

The second is central cyanosis, a bluish colour of the lips and tongue that signals low oxygen. It was seen in only about 3 in every 100 babies, but when present it was strongly linked to death and infection [1]. A bluish tinge can be harder to see in babies with darker skin, and the lips and tongue are the best places to look when an oxygen-measuring device is not available [16].

What this means for families

Most babies who have a cold, a fussy day or a single feed that goes badly are not seriously ill. In a large African community study, about 13 in every 100 babies showed at least one sign of infection in their first two months, and about 2 in every 100 of those babies died [17]. Most babies with a warning sign recover, which is why a prompt check by a health worker, rather than alarm, is the right response.

This research does, however, give parents and carers a clear list of changes that deserve urgent attention: a baby who stops feeding well, cries weakly or not at all, is unusually sleepy or hard to wake, feels cold, or looks blue around the lips or tongue should be seen by a health worker straight away. If you are unsure, it is always reasonable to ask. In hospitals, these signs are checked alongside blood tests and monitoring, and they help staff decide who needs treatment first. Related In[Neo]Sight articles explain how one programme worked to keep newborns warm and what causes newborn deaths worldwide.

It is also important to know what the study cannot say. It shows which signs tend to go together with serious illness, not that any single sign causes it, and it could not take into account things like how early a baby was born [1].

What researchers are working on next

The authors suggest that new studies should test whether adding slow capillary refill and a bluish colour to the checklist would help health workers find the sickest babies sooner, and whether computer-based approaches could make better use of the information a health worker gathers [1]. Any change must stay practical: health workers who use the IMCI programme already describe too little training and supervision and too little time with each family [18], and the programme is least fully in place in the countries where babies are most at risk [19].

For now, the message is reassuring as well as practical. The signs health workers already look for are supported by the evidence, and the changes a watchful parent can notice, in feeding, crying, alertness, warmth and colour, are all signs this review linked to serious illness, and several of them were among the most strongly linked, so they are worth acting on promptly.

References

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